1 //===-- ConstantFolding.h - Fold instructions into constants --------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file declares routines for folding instructions into constants when all 11 // operands are constants, for example "sub i32 1, 0" -> "1". 12 // 13 // Also, to supplement the basic VMCore ConstantExpr simplifications, 14 // this file declares some additional folding routines that can make use of 15 // TargetData information. These functions cannot go in VMCore due to library 16 // dependency issues. 17 // 18 //===----------------------------------------------------------------------===// 19 20 #ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H 21 #define LLVM_ANALYSIS_CONSTANTFOLDING_H 22 23 namespace llvm { 24 class Constant; 25 class ConstantExpr; 26 class Instruction; 27 class TargetData; 28 class Function; 29 class Type; 30 template<typename T> 31 class ArrayRef; 32 33 /// ConstantFoldInstruction - Try to constant fold the specified instruction. 34 /// If successful, the constant result is returned, if not, null is returned. 35 /// Note that this fails if not all of the operands are constant. Otherwise, 36 /// this function can only fail when attempting to fold instructions like loads 37 /// and stores, which have no constant expression form. 38 Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0); 39 40 /// ConstantFoldConstantExpression - Attempt to fold the constant expression 41 /// using the specified TargetData. If successful, the constant result is 42 /// result is returned, if not, null is returned. 43 Constant *ConstantFoldConstantExpression(const ConstantExpr *CE, 44 const TargetData *TD = 0); 45 46 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 47 /// specified operands. If successful, the constant result is returned, if not, 48 /// null is returned. Note that this function can fail when attempting to 49 /// fold instructions like loads and stores, which have no constant expression 50 /// form. 51 /// 52 Constant *ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 53 ArrayRef<Constant *> Ops, 54 const TargetData *TD = 0); 55 56 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 57 /// instruction (icmp/fcmp) with the specified operands. If it fails, it 58 /// returns a constant expression of the specified operands. 59 /// 60 Constant *ConstantFoldCompareInstOperands(unsigned Predicate, 61 Constant *LHS, Constant *RHS, 62 const TargetData *TD = 0); 63 64 /// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue 65 /// instruction with the specified operands and indices. The constant result is 66 /// returned if successful; if not, null is returned. 67 Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, 68 ArrayRef<unsigned> Idxs); 69 70 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 71 /// produce if it is constant and determinable. If this is not determinable, 72 /// return null. 73 Constant *ConstantFoldLoadFromConstPtr(Constant *C, const TargetData *TD = 0); 74 75 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 76 /// getelementptr constantexpr, return the constant value being addressed by the 77 /// constant expression, or null if something is funny and we can't decide. 78 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE); 79 80 /// canConstantFoldCallTo - Return true if its even possible to fold a call to 81 /// the specified function. 82 bool canConstantFoldCallTo(const Function *F); 83 84 /// ConstantFoldCall - Attempt to constant fold a call to the specified function 85 /// with the specified arguments, returning null if unsuccessful. 86 Constant * 87 ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands); 88 } 89 90 #endif 91
